The confocal microscope is widely used in many areas of biological and medical research because of its ability to image subsurface features with high resolution and contrast. The operating principle of a confocal scanning optical microscope (“CSOM”) is that an illuminating beam of light is scanned across a field of view from which only light emerging from a focal plane of an objective lens contributes to image formation. This differs from conventional light microscopy, wherein light from the focus plane of the objective lens, as well as from all out of focus planes across the entire field of view, is observed. In practice, the focal plane can be positioned below the surface of an opaque material for the non-destructive imaging of microscopic details at depth, or it may be positioned on the surface of a reflective material for observing high-resolution surface detail.
CSOMs are generally available in two basic configurations. The first scans a high intensity laser across the field of view with a computer compiling an image from the scan. These laser CSOM devices are generally too heavy and sensitive to motion to be portable. The second configuration uses a rotating “Nipkow” disk with a series of pinholes formed therein to transmit portions of an illuminating beam of light to and from the object to compile an image in real time. The image compiled from a Nipkow CSOM is generally visible through objective eyepieces without computer compilation.
Nipkow disks typically contain thousands of perforations (e.g., 32,000 or more), each having a diameter of about 50 microns. These perforations are generally arranged as a series of Archimedean spirals. In operation, the disk is spun to rotate the series of precisely aligned perforations across an incident light beam to create an incident light scan with returning light directed back through the disk. One available form of a Nipkow disk CSOM uses both sides of the rotating disk, e.g., one side for light passing to the specimen and the other side for light returning from the specimen. Because the precise alignment of multiple internal mirrors is required to obtain an accurate image, these instruments are very sensitive to motion and are not easily portable. In fact, even limited motion of such devices may require time consuming realignment of the mirrors. Although Nipkow disk CSOMs using only one side of the rotating disk for both purposes are less motion sensitive, current devices achieved the required base stability only through a heavy, non-adjustable base permanently mounted to the optics.